Re: [PATCH] do not limit locked memory when RLIMIT_MEMLOCK is RLIM_INFINITY

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 09 Jul 2007 17:59:12 -0700 Herbert van den Bergh <Herbert.van.den.Bergh@oracle.com> wrote:

> 
> [resending, since my previous message had tabs converted to spaces]
> 
> This patch fixes a bug in mm/mlock.c on 32-bit architectures that prevents
> a user from locking more than 4GB of shared memory, or allocating more
> than 4GB of shared memory in hugepages, when rlim[RLIMIT_MEMLOCK] is
> set to RLIM_INFINITY.
> 
> Signed-off-by: Herbert van den Bergh <herbert.van.den.bergh@oracle.com>
> Acked-by: Chris Mason <chris.mason@oracle.com>
> 
> --- linux-2.6.22/mm/mlock.c.orig	2007-07-09 10:19:31.000000000 -0700
> +++ linux-2.6.22/mm/mlock.c	2007-07-09 10:19:19.000000000 -0700
> @@ -244,9 +244,12 @@ int user_shm_lock(size_t size, struct us
>  
>  	locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
> +	if (lock_limit == RLIM_INFINITY)
> +		allowed = 1;
>  	lock_limit >>= PAGE_SHIFT;
>  	spin_lock(&shmlock_user_lock);
> -	if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
> +	if (!allowed &&
> +	    locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
>  		goto out;
>  	get_uid(user);
>  	user->locked_shm += locked;

OK.  Seems like a nasty bug if one happens to want to do that.  Should we
backport this into 2.6.22.x?

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